THE ACFT WAS FIRST OBSERVED MAKING LOW PASSES, ALMOST STRIKING TREES & POWER LINES. IT THEN CONTINUED IN A STEEP BANK THROUGH ABOUT 90 DEG OF TURN, ROLLED INVERTED & PITCHED DOWN SIMULTANEOUSLY. THE ACFT IMPACTED THE GROUND IN THE PARKINGLOT OF A CONVENIENCE STORE IN WHAT WAS DESCRIBED AS A 'STRAIGHT DOWN NOSE FIRST' ATTITUDE. TOXICOLOGICAL TESTS REVEALED ALCOHOL LEVELS OF 0.220% BLOOD, 0.229% URINE & 2.364% GASTRIC. AN UNBROKEN, HALF FULL BOTTLE OF LIQUOR WAS REMOVED FROM THE WRECKAGE. ON 1/30/83, AT 0410, THE PLT WAS SPOTTED FLYING RECKLESSLY AT A LOW ALTITUDE. SHERIFF'S DEPUTIES, WHO CONFRONTED THE PLT AFTER LANDING, STATED HE SMELLED OF ALCOHOL. HE WAS GIVEN A SOBRIETY TEST WHICH HE PASSED 'APPROXIMATELY AVERAGE.' ON 2/14/83 THE FAA SENT A LETTER TO THE PLT STATING THEY WERE INVESTIGATING THE INCIDENT. THE INVESTIGATION WAS CLOSED ON 5/5/83 WITH NO ACTION TAKEN.